Telescopic hydraulic cylinder

ABSTRACT

An extension cylinder is provided and includes an elongated tube having a distal end, a proximal end, and a first fluid opening formed proximate the proximal end. The extension cylinder also includes an elongated rod that is telescopically received within the elongated tube through the distal end thereof. The elongated rod has a second fluid opening formed proximate a rod distal end. A fluid communication tube is disposed between, and enables fluid communication between, the first and second fluid openings. The fluid communication tube includes a length that varies depending on how far the elongated rod is extended or retracted from the distal end of the elongated tube.

BACKGROUND OF THE INVENTION

[0001] The present application generally pertains to telescoping lift arms that may be utilized, either in pairs or as an individual arm, in the context of a loader, such as a skid steer loader. More specifically, the present application pertains to a hydraulic extension cylinder designed to hydraulically extend and retract a telescopic lift arm, while at the same time facilitating consistent fluid communication between a fluid tank (and/or a fluid pump) at a base end of the lift arm and a hydraulically actuated device located proximate a distal end of the lift arm.

[0002] Telescoping lift arms have been well known and used in various applications, including front-end loaders, crane booms, and the like. Certain of these known telescoping lift arms include a hydraulic extension cylinder that is configured to slide or telescope an inner lift arm section relative to an outer lift arm section in response to an instruction or signal. In this way, the over all length of the lift arm can be desirably adjusted.

[0003] Within certain applications, it becomes desirable to position a hydraulically actuated device (e.g., a tool) proximate a distal end of a telescoping lift arm. For example, the distal end of the telescoping lift arm may be configured to support a hydraulically actuated tree cutting tool, a cement mixing tool, an adjustable bucket, or some other hydraulically active device. In order to provide hydraulic power, a fluid communication path is typically provided to connect a fluid tank (and/or a fluid pump), generally located at a proximal end of the telescoping lift arm, with the hydraulically actuated device, generally located proximate a distal end of the of the telescoping lift arm.

[0004] It is desirable that a hydraulically actuated device located proximate a distal end of a telescoping lift arm remains operational regardless of the lift arm's extension status. Therefore, it is desirable to maintain continuous fluid communication between the fluid tank (and/or a fluid pump) and the hydraulically actuated device regardless of the extension status of the telescoping lift arm. Because the precise distance between the fluid tank (and/or a fluid pump) and the hydraulically actuated device varies depending on extension and retraction of the telescoping lift arm, maintaining continuous fluid communication presents a challenging design task.

[0005] One way to maintain the necessary continuous fluid flow regardless of the extension status of an associated telescoping lift arm is to provide a telescoping feed line between the tank (and/or a fluid pump) and the hydraulically actuated device. Accordingly, as the telescoping lift arm extends and retracts, so does the telescoping feed line. Incorporation of a telescoping feed line, however, requires specialized mechanical and hydraulic components that generally increase overall design costs. Also, due to the active mechanical nature of a telescoping feed line, a significantly increased maintenance burden is virtually inevitable.

[0006] The present invention provides a solution to these and other problems and offers advantages over the prior art.

SUMMARY OF THE INVENTION

[0007] One aspect of the present invention generally pertains to an extension cylinder that includes an elongated tube having a distal end, a proximal end, and a first fluid opening formed proximate the proximal end. The extension cylinder also includes an elongated rod that is telescopically received within the elongated tube through the distal end thereof. The elongated rod has a second fluid opening formed proximate a rod distal end. A fluid communication tube is disposed between, and enables fluid communication between, the first and second fluid openings. The fluid communication tube includes a length that varies depending on how far the elongated rod is extended or retracted from the distal end of the elongated tube.

[0008] Another aspect of the present invention generally pertains to an actuator rod for use within a hydraulic extension cylinder. The actuator rod includes a proximal end, a distal end and an exterior surface. A fluid opening is formed proximate the distal end. A tube-receiving opening is formed proximate the proximal end. A fluid chamber is formed by an interior surface of the elongated rod. The fluid chamber is connected to, and extends between, the fluid and tube-receiving openings. A piston is engaged proximate the proximal end of the actuator rod. The piston has a piston opening configured to accommodate and prevent significant obstruction of the tube-receiving opening.

[0009] Still another aspect of the present invention generally pertains to a power machine that includes a frame, a plurality of ground engaging wheels that support the frame, and a cab that is operably coupled to the frame and defines an operator compartment. In addition, an engine is operably coupled to the wheels and a telescoping lift arm is operably coupled to the frame. A hydraulically actuated device is secured to the power machine proximate a distal end of the telescoping lift arm. A hydraulic cylinder is attached to a portion of the telescoping lift arm for extension and retraction, while at the same time providing a path for fluid communication to the hydraulically actuated device. The hydraulic cylinder includes an elongated tube having a distal end, a proximal end, and a first fluid opening formed proximate the proximal end. An elongated rod is telescopically received within the elongated tube through the distal end thereof. The elongated rod has a second fluid opening formed proximate a rod distal end. A fluid communication tube is disposed between, and enables fluid communication between, the first and second fluid openings. The distance between the first and second fluid openings varies depending on how far the elongated rod is extended or retracted form the distal end of the elongated tube.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a schematic side elevational view of a skid steer loader having a specialized lift arm assembly for extending and retracting a telescoping loader arm.

[0011]FIG. 2 is an exploded perspective view of the specialized lift arm assembly.

[0012]FIG. 3 is a top plan view of the specialized lift arm assembly.

[0013]FIG. 4A is a side view of an actuator cylinder made according to the present invention.

[0014]FIG. 4B is an end view of the actuator cylinder and is depicted from the perspective of line 4B-4B in FIG. 4A.

[0015]FIG. 4C is an end view of the actuator cylinder and is depicted from the perspective of line 4C-4C in FIG. 4A.

[0016]FIG. 5 is a cross-sectional view of the actuator cylinder taken along line 5-5 in FIGS. 4B and 4C.

[0017]FIG. 6A is a side view of a portion of an actuator cylinder that includes a rod extension piece.

[0018]FIG. 6B is a cross-sectional view of the components depicted in FIG. 6A and is taken through line 6B-6B in FIG. 6A.

[0019]FIG. 7A is a side view of a portion of an actuator cylinder that includes a rod extension piece.

[0020]FIG. 7B is a cross-sectional view of the components depicted in FIG. 7A and is taken through line 7B-7B in FIG. 7A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021]FIG. 1 is a schematic representation of a skid steer loader 10 having a telescoping loader arm (also known as a loader boom). Skid steer loader 10 includes specialized lift arm assemblies for extending and retracting the telescoping loader arm. FIG. 2 is an exploded view of the specialized lift arm assemblies incorporated into skid steer loader 10. FIG. 3 is a top plan view of the specialized lift arm assemblies.

[0022] It should be noted that skid steer loader 10 includes telescoping lift arms having a bell-shaped cross section that permits an inner lift arm to slide or telescope relative to an outer lift arm while being guided along linear bearings. This particular telescopic lift arm arrangement, which should be considered only one illustrative arrangement of many that are suitable to accommodate embodiments of the present invention, is described specifically in co-pending U.S. application Ser. No. 10/123,469, filed on Apr. 15, 2002, and entitled “TELESCOPING LOADER LIFT ARM.”

[0023] Skid steer loader 10 has a frame 12, and drive wheels 14 for propelling the loader across the ground. Frame 12 supports an operator's cab 16, and an engine compartment 18 for housing the engine (not shown). The frame 12 also includes boom support plates or frame members 20 on which a telescoping lift arm assembly 22 is pivotally mounted on pivots 36. The lift arm assembly 22 comprises individual lift arms 24 and 26, one pivoted on each of the opposite sides of the skid steer loader. The two lift arms are illustratively identical except that one is on the right-hand side and the other is on the left-hand side.

[0024] The lift arm assembly 22 is made up of an individual inner lift arm tube 42 that is held in a complementary-shaped outer arm tube 40. The inner tubes 42 are held together with a suitable cross member 28 proximate their forward ends. The outer arm portion of lift arm assembly 22 is raised and lowered by pivoting the lift arm assembly about the pivots 36 with hydraulic cylinders 30 that have base end pivots 32 connected to the vehicle frame, and rod ends connected at pivots 34 to the lift arms 24 and 26. The actuators 30 are controlled in a conventional manner using suitable valves in the hydraulic system of the skid steer loader.

[0025] Each of the telescoping tubular lift arms 24 and 26 includes the main outer lift arm tube or housing 40 and the telescoping inner lift arm tubes 42. The inner lift arm tubes 42 telescope relative to the outer lift arm tubes 40 as an inner assembly 29. The lift arm tubes 42 fit inside the outer lift arm tubes 40 and slide longitudinally relative thereto. The inner assembly 29 of the inner lift arm tubes is moved as a unit through the use of hydraulic actuators 44 in a conventional manner. A collar 40C is provided proximate the end of outer lift arm tubes for reinforcing and adding rigidity to the side walls of the outer tube.

[0026] As shown, the base ends of actuators 44 are mounted to the outer lift arm housing or tubes 40 on pins 44A, so that the actuators 44 pivot up and down therewith. Each actuator 44 has a rod end pivotally connected with pins 48 to the inner lift arm tubes 42 so that upon extending and retracting the actuator cylinders 44 with a suitable valve 45, the inner lift arm tubes 42 are extended and retracted as desired. The inner lift arm tube assembly 29, as shown, has a tool or accessory attachment connection plate 52 proximate its outer or forward ends. Depending side frames 53, which are fixed to the inner lift arm tubes 42, are connected with a cross member 28. The attachment plate is pivotally mounted to the lower ends of the side frame 53 and optionally controlled with control cylinders 53A. Cross member 28 can be used for mounting a hydraulic valve. In accordance with one embodiment, a hydraulically actuated device is mounted on the distal end of the loader arms (e.g., mounted to the attachment plate) and operably connected to a hydraulic valve mounted on cross member 28.

[0027] The hydraulic actuators 44 in FIGS. 1-3 are merely representative of the types of actuators that can be used to enable telescoping movement of the inner lift arm tubes. Embodiments of the present invention pertain to specialized hydraulic actuators that can be used to enable telescoping movement of the inner lift arm tubes, while at the same time providing a fluid communication path to and/or from a hydraulically-actuated device positioned proximate a distal end of the telescoping lift arm. These specialized hydraulic actuators are described below in detail.

[0028]FIG. 4A is a side view of an actuator cylinder 400, in accordance with an embodiment of the present invention. Generally speaking, actuator cylinder 400 is configured to extend and retract a telescoping lift arm, while at the same time providing a fluid communication path to and/or from a hydraulically-actuated device positioned proximate a distal end of the telescoping lift arm. Actuator cylinder 400 is illustratively of an overall configuration making it appropriate to be incorporated as a hydraulic actuator 44 within skid steer loader 10 (FIGS. 1-3).

[0029] Actuator cylinder 400 has a base end member 402 that is configured to be pivotally connected to outer lift arm tube 40 on a pin connection 44A such that cylinder 400 is able to pivot up and down with the tube. Base end member 402 is connected to a proximal end of a tube 408. Cylinder 400 further includes a rod end member 404 that is configured to be pivotally connected with a pin connection 48 to an inner lift arm tube 42. Rod end member 404 is connected to a distal end 418 of a rod 420. Rod 420 extends through and is slidably and telescopically engaged within tube 408.

[0030] A proximal end of rod 420 is connected to a piston (not shown in FIG. 4) that is controlled in a conventional manner using a suitable valve or valves within the hydraulic system of the skid steer loader (e.g., valve 45 in FIG. 1) so as to enable rod 420 to be desirably extended and retracted. Tube 408 includes fluid conduit openings 414 and 416 through which fluid is transferred to desirably drive the piston in one direction or the other, thereby causing rod 420 to extend and retract as described. In this way, in the context of skid steer loader 10, the inner lift arm tube 42, which is connected to rod end member 404, can be telescopically extended or retracted, thereby causing a corresponding extension or retraction of the associated lift arm.

[0031] In accordance with one embodiment of the present invention, an actuator cylinder 400 is incorporated with a lift arm on both sides of skid steer loader 10. In other words, one actuator cylinder 400 is utilized to telescopically extend or retract the lift arm on the right-hand side of loader 10 and another is utilized in association with the lift arm on the left-hand side. In accordance with another embodiment, however, an actuator cylinder 400 is only used on one side or the other.

[0032] In addition to enabling actuation of a telescopic lift arm, actuator cylinder 400 also provides a fluid communication path to and/or from a distally positioned hydraulically actuated device. Accordingly, a first fluid conduit opening 410 is formed within a proximal end 411 of actuator cylinder 400. A second fluid conduit opening 412 is formed within a distal end 413. Fluid conduit opening 410 is configured to be in fluid communication with fluid conduit opening 412, even during and following an extension or retraction of rod 420. Fluid conduit opening 410 is configured for direct or indirect connection to a fluid tank (and/or a fluid pump). An indirect connection, for example, is made utilizing an intermediate hose and/or a valve or valve box. Fluid conduit opening 412 is configured for connection to a hydraulically actuated tool. The connection between fluid conduit opening 412 and the hydraulically actuated tool is illustratively made either directly or indirectly (e.g., indirectly through a hose and/or through an associated hydraulic valve or valve box mounted on cross member 28 shown in FIG. 1).

[0033] As will be described in more detail in relation to FIG. 5, fluid is communicated between conduit openings 410 and 412 through chambers formed within rod 420 and an internal tube member. Fluid communication between conduit openings 410 and 412 through the chambers remains uninterrupted during and following an extension or retraction of rod 420. Illustratively, the stroke of the piston within actuator cylinder 400, and/or the length of rod 420, can be customized to accommodate a desired range of extension and retraction that can be accomplished without interruption of fluid communication between conduit openings 410 and 412. Specific structural strategies for customizing the length of rod 420 will be discussed below in relation to FIGS. 6A, 6B, 7A and 7B. Through incorporation and customization of an actuator cylinder 400, a hydraulically actuated device located proximate a distal end of skid steer loader 10's telescoping lift arms is able to remain in operable fluid communication with a fluid tank (and/or a fluid pump) generally regardless of the extension status of an associated telescoping lift arm.

[0034] Different hydraulic valves and hydraulically actuated devices require different fluid flow schemes. It is within the scope of the present invention to specifically adapt one or more actuator cylinders 400 to accommodate different fluid flow schemes. In accordance with one embodiment, the actuator cylinder 400 on the right-hand side provides a fluid communication path to a hydraulically-actuated device positioned proximate a distal end of the telescoping lift arm, while the other actuator cylinder provides a return fluid communication path away from the hydraulically-actuated device, or vice versa. In accordance with another embodiment of the present invention, however, at least one and illustratively both actuator cylinders 400 are configured to provide a reversible fluid communication path to and from a hydraulically-actuated device positioned proximate a distal end of the telescoping lift arm (e.g., two-way switchable fluid communication).

[0035]FIG. 4B is an end view of actuator cylinder 400 as viewed from the perspective of line 4B-4B in FIG. 4A. An end view of actuator cylinder as viewed from the perspective of line 4C-4C in FIG. 4A is depicted by FIG. 4C. FIG. 5 is a cross-sectional view of actuator cylinder 400 taken along line 5-5 in FIGS. 4B and 4C.

[0036] With reference to FIG. 5, a proximal end 502 of rod 420 is connected to a piston 504. Piston 504 is connected to (e.g., inertia welded to) rod 420. In addition, piston 504 slidably engages an interior surface of tube 408. Accordingly, piston 504 divides a fluid chamber 505 into two portions, namely, a first portion that is proximally located relative to piston 504 and a second portion that is distally located relative to piston 504. An O-ring, a nylon seal, a wear ring and/or some other similar device can illustratively be integrated with piston 504 to enhance the ability of piston 504 to move within fluid chamber 505 while still isolating the first and second portions of the fluid chamber from one another.

[0037] The portion of fluid chamber 505 that is distally located relative to piston 504 is illustratively in fluid communication with conduit opening 414 (FIG. 4A). The portion of fluid chamber 505 that is proximally located relative piston 504 is illustratively in fluid communication with conduit opening 416 (FIG. 4A). Accordingly, as was described above in relation to FIG. 4A, fluid is transferred through conduit openings 414 and 416 in order to desirably drive piston 504 in one direction or the other, thereby causing rod 420 to extend or retract. Therefore, piston 504 is configured to be hydraulically driven by a suitable valve system (e.g., valve 45 in FIG. 1) so as to enable rod 420 to be desirably extended or retracted, thereby causing a corresponding extension or retraction of a lift arm.

[0038] A chamber 532 is formed within rod 420 and is generally formed by an internal surface of the rod. In accordance with one embodiment, chamber 532 illustratively extends from an opening 528 (formed through piston 504) to conduit opening 412. In accordance with another embodiment, however, chamber 532 terminates at the proximal end of rod end member 404, which includes a corresponding internal chamber that extends between its proximal and distal ends. An O-ring, lock nut, or some other sealing mechanism is optionally utilized to prevent leakage proximate the area where rod 420 adjoins rod end member 404. Whether rod 420 extends through rod end member 404 or cooperates with a separate channel formed within rod end member 404 is not critical to the present invention. Both designs enable a fluid communication path that reaches conduit opening 412.

[0039] An inner tube element 560, which includes an inner chamber 562, extends from conduit opening 410, through the piston opening 528 and into the rod chamber 532. Inner tube element 560 is sealingly engaged proximate piston 504 such that fluid flow is generally prevented between chamber 505 and the rod chamber 532, and between chamber 505 and the tube element chamber 562. Inner tube element 560 is also slidingly engaged proximate piston 504.

[0040] In accordance with one embodiment, inner tube element 560 terminates proximate the distal end of end member 402. Accordingly, end member 402 includes a corresponding internal chamber that extends between its proximal and distal ends. An O-ring, lock nut or some other sealing mechanism is optionally utilized to prevent leakage proximate the area where inner tube element 560 adjoins end member 402. Whether inner tube element 560 extends through end member 402 or cooperates with a separate channel formed within end member 402 is not critical to the present invention. Both designs enable a fluid communication path that reaches conduit opening 410.

[0041] Inner tube element 560 illustratively has an overall length that enables a distal end 564 thereof to remain within the rod chamber 532 regardless of the position of piston 504 within chamber 505. Accordingly, fluid can be transferred between conduit openings 410 and 412 regardless of whether rod 420 is fully extended, fully retracted, or somewhere in between. Regardless of the extension status of rod 420, fluid can be transferred between chamber 562 and fluid chamber 532, and therefore between conduit openings 410 and 412, and therefore between a fluid tank (and/or a fluid pump) at a base end of the lift arm and a hydraulically actuated device located proximate a distal end of the lift arm.

[0042] In FIGS. 4A-4C and 5, rod 420 is directly connected to rod end member 404. In accordance with one embodiment, this connection is made utilizing a thread/seal interface. For example, the distal end of the rod includes threads that correspond to threads in the end member. An O-ring and/or some other fluid sealing device can be utilized to seal and secure the cooperating threaded components. Other means for attaching rod 420 to rod end member 404 are within the scope of the present invention.

[0043] Chamber 562 and chamber 532 together form a fluid communication tube that extends from a distal end of fluid chamber 532 to a proximal end of chamber 562. The distance between the distal end of fluid chamber 532 and the proximal end of chamber 562 will illustratively vary depending on how far tube 420 is extended or retracted (e.g., depending on how far distal end 564 is inserted into chamber 532). The distance between the distal end of fluid chamber 532 and the proximal end of chamber 562 may or may not include the chamber portions within ends 402 and 404 (e.g., depending on whether the chamber portions within ends 402 and 404 are integrally formed with chambers 532 and 562). Either way, the general length of the communication tube (e.g., chamber 532+chamber 562) will vary depending on how far tube 420 is extended or retracted.

[0044] For some applications, directly attaching the rod to the end member does not enable an economical cylinder and/or rod length. For these applications, in accordance with one aspect of the present invention, a low cost extension tube can be incorporated between the rod and end members (e.g, to reduce costs associated with long lengths of expensive material).

[0045]FIG. 6A, in accordance with one embodiment of the present invention, is a side view of a portion of an actuator cylinder that includes an actuator rod extension piece 602 and an associated rod extension coupler 604. FIG. 6B is a cross-sectional view of the components depicted in FIG. 6A and is taken through line 6B-6B in FIG. 6A. Elements identified in FIGS. 6A and 6B that are the same as or similar to elements identified and described in relation to previous Figures have been given a same or similar reference numeral.

[0046] Rod extension coupler 604 is illustratively utilized to align and connect distal end 418 of rod 420 with a proximal end 606 of rod extension piece 602. Lock nuts 608 facilitate and secure the connection of the rod ends. It should be pointed out that connection devices other than lock nuts (e.g., inertia welded joints, etc.) could be utilized without departing from the scope of the present invention. One or more O-ring seals 610 are optionally and internally positioned between rod end 610 and coupler 604, and between rod end 418 and coupler 604, so as to prevent fluid leakage proximate coupler 604. A distal end 612 of rod extension piece 602 is connected and secured to rod end member 404 utilizing a lock nut 614. An optional O-ring seal 616 is internally positioned between rod end 612 and end member 404 to prevent fluid leakage.

[0047] Rod extension piece 602 has an internal chamber 620 formed therein. After piece 602 has been secured in place utilizing coupler 604, chamber 620 is securedly positioned so as to be in fluid communication with chamber 532 and the chamber formed within rod end member 404. Accordingly, conduit opening 412 remains in fluid communication with chamber 532, regardless of the extension status of rod 420. In accordance with one embodiment, internal chamber 620 extends through rod end member 404 to conduit opening 412 (e.g., instead of engaging a chamber formed within rod end member 404).

[0048]FIG. 7A, in accordance with another embodiment of the present invention, is a side view of a portion of an actuator cylinder that includes an actuator rod extension piece 702. FIG. 7B is a cross-sectional view of the components depicted in FIG. 7A and is taken through line 7B-7B in FIG. 7A. Elements identified in FIGS. 7A and 7B that are the same as or similar to elements identified and described in relation to previous Figures have been given a same or similar reference numeral.

[0049]FIGS. 7A and 7B depict another embodiment wherein a rod extension piece 702 is directly connected to distal end 418 of rod 420, without incorporation of a coupler component. The distal end 418 illustratively includes threads that are designed to engage corresponding threads formed within the proximal end 706 of rod extension piece 702. A lock nut 704 facilitates and secures the connection of the rod ends. An optional sealing member 708 (e.g., a ring seal or an O-ring) is optionally and internally placed between the component ends to prevent fluid leakage at the point of connection. Connection devices other than a threaded engagement and/or a lock nut arrangement could be utilized without departing from the scope of the present invention. A distal end 712 of rod extension piece 702 is connected and secured to rod end member 404 utilizing an inertia weld attachment or some other means of attachment (e.g., a threaded engagement, lock nut, etc.). An optional O-ring seal can be internally positioned between rod end 712 and end member 404 to prevent fluid leakage.

[0050] Rod extension piece 702 has an internal chamber 720 formed therein. After piece 702 has been secured in place, chamber 720 is in fluid communication with chamber 532 and the chamber formed within rod end member 404. Accordingly, conduit opening 412 remains in fluid communication with chamber 532, regardless of the extension status of rod 420. In accordance with one embodiment, internal chamber 720 extends through rod end member 404 to conduit opening 412 (e.g., instead of engaging a chamber formed within rod end member 404).

[0051] Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. 

What is claimed is:
 1. An extension cylinder, comprising: an elongated tube having a distal end, a proximal end, and a first fluid opening formed proximate the proximal end; an elongated rod that is telescopically received within the elongated tube through the distal end thereof, the elongated rod having a second fluid opening formed proximate a rod distal end; and a fluid communication tube disposed between, and enabling fluid communication between, the first and second fluid openings, wherein the fluid communication tube includes a length that varies depending on how far the elongated rod is extended or retracted from the distal end of the elongated tube.
 2. The extension cylinder of claim 1, wherein the fluid communication tube comprises: a first fluid chamber formed by an interior surface of the elongated rod; and a second fluid chamber formed by an interior surface of an internal tube member that is positioned within the elongated tube, wherein at least a portion of the internal tube member extends into the first fluid chamber, the internal tube member and the first fluid chamber being configured such that the amount of the internal tube member that extends into the first fluid chamber varies depending on how far the elongated rod is extended or retracted from the distal end of the elongated tube, thereby enabling uninterrupted fluid communication between the first and second fluid openings during and following an extension or retraction of the elongated rod.
 3. The extension cylinder of claim 2, wherein the elongated tube further comprises a tube interior surface that forms an extension chamber, the internal tube member and the elongated rod being radially displaced from the tube interior surface.
 4. The extension cylinder of claim 3, further comprising a piston attached to the elongated rod, the piston being slidably received within the extension chamber.
 5. The extension cylinder of claim 1, wherein the elongated tube further comprises a tube interior surface that forms an extension chamber, said fluid communication tube being radially displaced from the tube interior surface.
 6. The extension cylinder of claim 5, further comprising a piston attached to the elongated rod and dividing the extension chamber into first and second portions, the piston being configured to extend or retract the elongated rod in response to fluid being added and subtracted to the first and second portions of the extension chamber.
 7. The extension cylinder of claim 1, further comprising a base end member that is attached to the proximal end of the elongated tube and includes a fluid conduit opening and a fluid chamber formed by an interior surface, wherein the fluid chamber extends between, and enables fluid communication between, the fluid conduit opening and the first fluid opening formed proximate the proximal end of the elongated tube.
 8. The extension cylinder of claim 1, further comprising a base end member that is attached to the proximal end of the elongated tube, wherein the fluid communication tube extends through the base end member.
 9. The extension cylinder of claim 1, further comprising a rod end member that is attached to the distal end of the elongated rod and includes a fluid conduit opening and a fluid chamber formed by an interior surface, wherein the fluid chamber extends between, and enables fluid communication between, the fluid conduit opening and the second fluid opening.
 10. The extension cylinder of claim 1, further comprising: a rod end member that includes a fluid conduit opening that is connected to a fluid chamber formed by an interior surface, wherein the fluid chamber extends through the rod end member and enables fluid communication to the fluid conduit opening; a rod extension piece that is secured between the distal end of the elongated rod and the rod end member, wherein the rod extension piece includes an extension fluid chamber formed by an interior surface, and wherein the extension fluid chamber extends between, and enables fluid communication between, the second fluid opening and the fluid conduit opening.
 11. The extension cylinder of claim 10, wherein an extension coupler is secured between the distal end of the elongated rod and the rod extension piece to facilitate connection of the rod extension piece to the distal end of the elongated rod.
 12. The extension cylinder of claim 1, further comprising a rod end member that is attached to the distal end of the elongated rod, wherein the fluid communication tube extends through the base end member.
 13. An actuator rod for use within a hydraulic extension cylinder, comprising: a proximal end and a distal end; an exterior surface; a fluid opening formed proximate the distal end; a tube-receiving opening formed proximate the proximal end; a fluid chamber formed by an interior surface of the elongated rod, the fluid chamber being connected to, and extending between, the fluid and tube-receiving openings; and a piston engaged proximate the proximal end and having a piston opening configured to accommodate and prevent significant obstruction of the tube-receiving opening.
 14. The actuator rod of claim 13, further comprising a rod end member that is attached to the distal end and includes a fluid conduit opening and a fluid chamber formed by an interior surface, wherein the fluid chamber extends between, and enables fluid communication between, the fluid conduit opening and the fluid opening.
 15. The actuator rod of claim 13, further comprising: a rod end member that includes a fluid conduit opening that is connected to a fluid chamber formed by an interior surface, wherein the fluid chamber extends through the rod end member and enables fluid communication to the fluid conduit opening; a rod extension piece that is secured between the distal end of the actuator rod and the rod end member, wherein the rod extension piece includes an extension fluid chamber formed by an interior surface, and wherein the extension fluid chamber extends between, and enables fluid communication between, the fluid opening of the actuator rod and the fluid conduit opening of the rod end member.
 16. The actuator rod of claim 15, wherein an extension coupler is secured between the distal end of the actuator rod and the rod extension piece to facilitate connection of the rod extension piece to the distal end of the elongated rod.
 17. The actuator rod of claim 13, further comprising a rod end member that is attached to the distal end of the actuator rod, wherein the fluid chamber formed by an interior surface of the elongated rod extends through the base end member.
 18. A power machine, comprising: a frame; a plurality of ground engaging wheels supporting the frame; a cab operably coupled to the frame and defining an operator compartment; an engine operably coupled to the wheels; a telescoping lift arm operably coupled to the frame; a hydraulically actuated device secured to the power machine proximate a distal end of the telescoping lift arm; and a hydraulic cylinder that is attached to a portion of the telescoping lift arm for extending and retracting the telescoping lift arm, while at the same time providing a path for fluid communication to the hydraulically actuated device, comprising: an elongated tube having a distal end, a proximal end, and a first fluid opening formed proximate the proximal end; an elongated rod that is telescopically received within the elongated tube through the distal end thereof, the elongated rod having a second fluid opening formed proximate a rod distal end; and a fluid communication tube disposed between, and enabling fluid communication between, the first and second fluid openings, wherein the distance between the first and second fluid openings varies depending on how far the elongated rod is extended or retracted form the distal end of the elongated tube.
 19. The power machine of claim 18, wherein the fluid communication tube comprises: a first fluid chamber formed by an interior surface of the elongated rod; and a second fluid chamber formed by an interior surface of an internal tube member that is positioned within the elongated tube, wherein at least a portion of the internal tube member extends into the first fluid chamber, the internal tube member and the first fluid chamber being configured such that the amount of the internal tube member that extends into the first fluid chamber varies depending on how far the elongated rod is extended or retracted from the distal end of the elongated tube, thereby enabling uninterrupted fluid communication between the first and second fluid openings during and following an extension or retraction of the elongated rod.
 20. The power machine of claim 18, wherein the elongated tube further comprises a tube interior surface that forms an extension chamber, said fluid communication tube being radially displaced from the tube interior surface. 